Boeing 787 problems still stump investigators

As the probe of burning batteries aboard Boeing Co.'s
BA, +0.81%
787 jets stretches into its second month, an international team of air-accident sleuths remains stumped about the underlying cause, according to people familiar with the details. This has fueled pessimism about how quickly the planes can resume flying.

Investigative activity remains intense, and a breakthrough could still come. But in the past few days, industry and government officials familiar with the probes on both sides of the Pacific have stressed the lack of progress. At a recent Department of Transportation briefing, according to one of these officials, government experts acknowledged "they may not be any closer to identifying root cause than they were" at the start of the National Transportation Safety Board's high-profile investigation.

After painstakingly dissecting a number of batteries, examining associated electronic parts, and analyzing information from flight-data records, NTSB experts and their Japanese counterparts haven't been able to pinpoint any specific component, automated subsystem or software application that appears to offer hope of finding answers.

With no apparent, clear-cut theory, investigators are now delving into additional parts of the plane's electrical grid. They also are seeking help from technical experts outside the aviation industry, including scientists and electronics engineers from the U.S. Navy and Department of Energy.

The initial probe began Jan. 7, after a lithium-ion battery aboard a Japan Airlines Co. (9201.TO) 787 parked at Boston's Logan International Airport ruptured and burst into flames. Nine days later, an All Nippon Airways Co. (9202.TO) Dreamliner on a domestic flight made an emergency landing and evacuation due to an overheating battery, prompting swift world-wide grounding of Boeing's flagship jets.

Initially, some involved with the investigation hoped finding a solution might take mere days. Now airlines and others are bracing for a delay that could stretch additional weeks, or even months. Barring a breakthrough, some pessimists predict that designing and installing a new battery system could take as long as a year.

United Continental Holdings Inc.
UAL, -0.79%
has slotted in other planes for its 787 routes through late February, and Japan Airlines has postponed the start--originally scheduled for the end of this month--of a new Tokyo-to-Helsinki route using the Dreamliner.

A spokeswoman for NTSB on Friday said "our investigators are moving swiftly and we are making progress," but she declined to elaborate. The Federal Aviation Administration's press office also declined to comment.

The NTSB has said it found short-circuits and evidence of uncontrolled overheating inside the fire-ravaged battery of the Japan Airlines 787. But what they still can't decipher is cause and effect.

"The short circuit, the fire, these are all symptoms that something is wrong," Deborah Hersman, the safety board's chairman, told reporters late last month. "These events should not happen as far as [the] design of the airplane."

Boeing has assigned hundreds of its own technical staff to work with the loosely coordinated U.S. and Japanese probes. The company's efforts using simulators to recreate battery-system malfunctions on the ground haven't provided significant new leads, according to one person close to the effort. Analysis of battery operating trends before the planes were grounded hasn't yielded major findings either, according to others closely tracking that data.

Boeing spokesman Marc Birtel says the company is "working around the clock with the sole focus of resolving the issue and returning the 787 fleet to flight status. Everyone is working to get to the answer as quickly as possible and good progress is being made."

Boeing Chief Executive Jim McNerney said last week that hundreds of experts are narrowing down possible explanations but haven't found a root cause. "When we know the answer," he said, "then we'll act on it."

Meanwhile, the Chicago plane maker is mulling potential contingency plans, according to people familiar with those options. One possible interim fix Boeing engineers have considered would place the 63-pound battery inside a containment box that would both protect nearby equipment and vent smoke overboard in the event of a failure, according to one person familiar with the proposal.

Boeing faces an uphill battle to get such a system approved, however, because federal investigators have sketched out a zero-tolerance approach when it comes to aircraft fires. So far, FAA officials have balked at engaging in any detailed discussions of potential interim fixes, according to people familiar with the matter, until experts succeed in recreating battery malfunctions under laboratory conditions.

The FAA appears poised to approve some flight tests, after a Boeing request emphasizing that there hasn't been a breakthrough from ground testing, according to people familiar with the request.

If the probes linger and pressure builds to get the planes back in the air, regulatory precedent could work in Boeing's favor. FAA safety rules account for fan blades of a jet engine possibly failing under extremely rare circumstances, but the casing that surrounds the front of the engine must contain all internal parts that break off without damaging the rest of the aircraft.

Write to Andy Pasztor at andy.pasztor@wsj.com and Jon Ostrower at jon.ostrower@wsj.com

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